Ok, so you have an operational solar power plant.

And you also have the generation reports related to the power plant, which details monthly generation from the solar power plant which is given in units

Now, how do you know whether the generation is in accordance with the industry standards?

Most would suggest you to cross check your solar power plant’s generation data with that of another power plant in the nearby region.

Solar power plant performance is usually measured with two metrics, CUF and Performance Ratio obtained for the power plant.

 To know more about what the average CUF from your solar power plant should be, click the below link:


To know more about performance ratio and associated guarantees, click below:


What do I need to know while analysing the generation data from the plants apart from the CUF and PR obtained?

  • The generation should be in accordance with the sunshine availability in the region:

Sunshine availability of your region has a tremendous impact on the expected generation from the solar power plant.

 For e.g., if the solar power plant is located close to the equatorial belt (like India), the power plant may be subject to a high amount of irradiance from the sun which can be quantified by a metric called the DNI (Direct Normal Irradiance). The Direct Normal Irradiance (DNI), a measure of solar radiation, will be above 5.5 kWh/m2/day for these regions. And in such cases, you can expect a generation of 4.5 to 5 units per kW from the solar system.

In countries with a moderate climate (with medium sunshine availability), the DNI range is usually between 3.5-5.5 5 kWh/m2/day. In such cases, expected generation is about 3.5-4 kWh per day per kW for these regions.

In cold countries like Canada, the sunshine availability through the year is pretty low. The DNI for these countries is usually lesser than 3.5 kWh/m2/day and one can expect a generation of about 2-3 units a day per kW from the solar system.

  • The generation will have seasonal variations

The numbers provided above are only an indicator of the average units that can be expected from the power plant. Realistically there could be variations in the generated units due to seasonal changes in the region.

Many people think that a hot sunny day will produce more electricity than a colder sunny day. This just isn’t the case. Solar PV relies on the light of the sun, but higher temperatures actually reduce the effectiveness of the panels. So cold and bright are actually ideal conditions.

Having said that, the lower the sun is in the sky, the less energy will reach the panels. In winter, the sun will always be lower in the sky, and therefore will produce that bit less energy. Couple that with the fact that winter days are shorter and unfortunately you can guarantee that the panels will not be as effective in winter.

This effect could be very drastic in countries with severe winters like Germany where the production will be around one-fifth of that during the summer seasons. However, in countries with tropical climates like India, the variation between summer and winter seasons will not be so significant. Solar Mango has analysed several generation reports and has come to a consensus that the generation during Nov-Dec from plants with medium to high sunshine availability would be about half to one-third of that during Aril-May.

  • The generation is dependent on the maintenance activities in the solar power plant

What we have seen at Solar Mango seems to suggest that in many dusty regions around the world that get rainfall only a few months a year, dust could cause significant decrease in generation. Based on some of the analyses Solar Mango made of real life solar power plant installations both at rooftops and solar farms, it can be said that solar panels that have not been cleaned at all for a year could lose as much as 15% of the output compared to regularly (once in 2 weeks) cleaned solar panels.

Over and above the maintenance practices, the use of extended monitoring systems, wise selection of key components, high quality design, etc. can also cause a significant variation in generation between solar power plants.

You might want to check these questions on Solar Power Plant Evaluation – Plant Performance

  • What is the average CUF (Capacity Utilisation Factor) of the power plant?-Here
  • What are the performance guarantees provided by the installer?-Here
  • What have been the cleaning practices for the panels over the years?-Here
  • What are the O&M practices followed?-Here
  • How do you check the quality of the  O&M company and personnel? – Here
  • What are the innovations employed in the power plant? How can they impact your  financial returns?-Here
  • Is there scope for expansion of the power plant, in terms of scale?-Here
  • What were the key problems the power plant had faced and what were the causes for these?-Here